Apple Pay is coming to Britain in July in its first expansion outside of North America, Apple confirmed at its annual worldwide developer conference.

Sometime in July, users of the iPhone 6 and 6 Plus, as well as Apple Watch owners, will be able to start making payments in shops around the country using their mobile phones.

Which banks are supported?

Just having a compatible device isn’t enough – you also need to have a credit or debit card and an account at a supporting bank. The first wave of banks to support the payment system include First Direct, HSBC, NatWest, Nationwide Building Society, Royal Bank of Scotland, Santander and Ulster Bank. Apple promises a second wave by the autumn, including Bank of Scotland, Coutts, Halifax, Lloyds Bank, MBNA, M&S Bank and TSB Bank.

Notably absent from that list is Barclays, which tweeted after the announcement to tell customers that “we’ve been talking with Apple about how our customers could use Apple Pay in addition to our existing mobile and payment services, and that [sic] these talks remain constructive”.

Where can you use it?

The technology Apple Pay is built on is fundamentally backwards compatible with the existing infrastructure for contactless payments, says Mastercard’s Mike Cowen, head of emerging payment products. That means there’s more than a quarter of a million establishments that will support the payment service from day one, including the entirety of Transport for London’s network, and major chains such as Pret a Manger, McDonald’s UK, Wagamama and Nando’s.

The majority of locations that take Apple Pay will be subject to the same limits that exist for conventional contactless payments, Cowen explains, because those limitations are hard-coded into the reader. That includes a limit of £20 per transaction, which will rise to £30 per transaction in September, because currently anything higher must be bought with a chip-and-pin card for the added security.

But a few chains have installed newer hardware that supports high value contactless payments, such as by Apple Pay, which are secured using biometric information such as fingerprints.

As well as a physical payment service, Apple Pay also lets users make in-app payments without having to re-enter their credit card information or share sensitive personal details with the company. The in-app payments also work on Apple’s two newest iPads, the iPad Air 2 and iPad Mini 3. Amongst the launch partners for that aspect of the service are: Addison Lee, Airbnb, Argos, Booking.com, British Airways, Domino’s, easyJet, Hailo, HotelTonight, hungryhouse, JD Sports, Just Eat, lastminute.com, Miss Selfridge, Ocado, Stubhub, thetrainline.com, Top10, Topshop, Uncover, Vueling, YPlan, Zalando and Zara.

How is it secured?

On most devices, Apple Pay requires authentication through Apple’s TouchID fingerprint scanners before it will authorise a payment. The only exception is the Apple Watch, which remains permanently unlocked and authenticated while on its owner’s wrist, but needs a passcode if it is taken off before it can be used to make a payment.

The actual transactions are secured using the new “digital secure remote payment” standard, which ensures that the actual credit card data is never transferred over to a merchant. Instead, a single-use “cryptogram” is sent to the merchant, which authorises one transaction of a specified amount – unlike normal credit card information, which can be reused again and again to authorise transactions.